Emilia Hanna, air pollution campaigner for Friends of the Earth Scotland, said: "Once again, streets in Scotland have dangerous levels of toxic air pollution which are breaking legal limits.

"The situation across Scotland is potentially showing some slow signs of improvements, but filthy streets continue to poison our lungs nearly a decade after a legal deadline.

"Scotland's first Low Emission Zone will be in Glasgow by the end of this year, and this will be an important test of commitment to address this problem.

"The rest of Scotland is looking to Glasgow to set a high standard with its Low Emission Zone."

A Scottish Government spokeswoman said: "We have committed to introducing Low Emission Zones (LEZs) into Scotland's four biggest cities between 2018 and 2020, and then into all other Air Quality Management Areas by 2023 where the National Low Emission Framework (NLEF) appraisals support such mitigation.

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"We will continue to work with industry to phase out the need for new petrol and diesel cars and vans by 2032.

"We have invested more than £210 million in active travel since the start of the 2011 spending review, and the most recent Programme for Government announced that we would double the active travel budget from £40 million to £80 million in 2018-19."

She added: "Our Cleaner Air for Scotland strategy sets out an ambitious programme of action to promote air quality and Scotland is the first country in Europe to pass legislation based on World Health Organisation guidelines for fine particulate matter."